Image forming apparatus such as coppying machines generally have a plurality of paper feed cassettes, that is, a paper feed cassette for every size of copy paper to be used. When feeding paper using such a paper feed cassette, it is preferable, in consideration for feeding speed, to feed paper laterally oriented (hereinafter referred to as "lateral feeding") rather than paper longitudinally oriented (hereinafter referred to as "longitudinal feeding"), with respect to the feeding direction. In some conventional copying machines, large size papers such as B4 size paper and A3 size paper are fed laterally for the above reason.
The lateral feeding of large size paper, however, brings about such a drawback that the sizes of parts disposed in a copying machine such as a photoreceptor drum, delivery roller, delivery path for paper are enlarged, increasing the production cost. Therefore, such a method is adapted in standard type copying machines that large size papers such as B4 size and A3 size papers are longitudinally fed while A4 size paper and smaller ones are laterally fed. When using a copying machine with a variable magnification function for performing reduced and enlarged copying operations, paper feed cassettes of B5R size and A4R sized used for longitudinal feeding are needed in order to perform image reduction, and paper feed cassettes of B5 size and A4 size used for lateral feeding are also needed when taking the feeding speed into consideration (the cassettes such as A4R and B5R are used for "longitudinal feeding " and the cassettes such as A4 and B5 are for "lateral feeding"). It is, however, required for using various types of paper feed cassettes to enlarge the size of a copying machine or replace one cassette with another according to purposes when copying. As a result, the parts of the copying machine become large, increasing the production cost in the former case, and the operation becomes more complicated and troublesome in the latter.
An image forming apparatus designed to solve the above problems is disclosed in Japanese Publication for Unexamined Patent Application Nos. 59245/1981 and 123859/1984, in which one cassette is used for both longitudinal feeding and lateral feeding by rotating the cassette. More specifically, a B5 size cassette is used as a B5 size cassette, and an A4 size cassette is used as an A4R size cassette.
In the above apparatus, the rotatable cassettes are rotated in response to the actuation of a cassette rotation key for executing the rotation of a rotatable cassette. Since such rotatable cassettes are required to be mounted on a rotation mechanism, the cassette is generally housed in the main body of an image forming apparatus.
With the use of the image forming apparatus having rotatable cassettes, whenever an operator depresses the cassette rotation key by mistake, the rotatable cassette is rotated. Therefore, the rotatable cassette is loaded with useless rotation and noise is produced at the time when the cassette is rotated. This not only breaks the silence in the surroundings but also reduces service life of the rotation mechanism.
Further, if the cassette rotation key is depressed during paper feeding from the rotatable cassette, a paper jamming often occurs. In case a paper jamming occurs, the rotatable cassette is rotated to return to an initial feeding station, and copying operation is peformed again to compensate for the deficient copies caused by the paper jamming. Thereafter, the cassette rotation key is depressed again in order to set the rotatable cassette in a desired feeding station. In this case, the rotatable cassette is forced to uselessly rotate like the foregoing case, causing the generation of noise and the deterioration of the durability of the rotation mechanism.
The above image forming apparatus is designed such that either one of the longitudinal feeding station and the lateral feeding station is set as a "preferential feeding station". When the power switch is turned on, or the rotatable cassette is inserted in the apparatus after supplying paper, if the rotatable cassette is out of the proper longitudinal feeding station or lateral feeding station, the rotatable cassette is rotated to be positioned in the preferential feeding station.
If paper is run out in the course of paper feeding from the rotatable cassette, and the rotatable cassette gets out of a predetermined feeding station when the rotatable cassette is inserted in the image forming apparatus after being taken out therefrom for paper supply, the rotatable cassette is rotated to be set in the preferential feeding station. If the originally set feeding station differs from the preferential feeding station, another operation for resetting the rotatable cassette in the originally set feeding station becomes necessary. This results in such a drawback that the efficiency in the operation is deteriorated.
The above image forming apparatus having (a) a plurality of rotatable cassettes, or (b) at least one rotatable cassette and one or more fixed cassettes is provided with a cassette selection key for selecting a cassette and cassette rotation keys for rotating a rotatable cassette. This increases the number of operation keys disposed on the operation panel and makes the key operation more troublesome.
Furthermore, in the case the width of the opening from which the rotatable cassette is taken out and inserted is limited, the rotatable cassette is required to be set in either of the feeding stations when being taken out or inserted. Therefore, if the rotatable cassette is positioned in a feeding station different from the station from which cassette insertion/taking out is only possible when copy paper is run out, the cassette is required to be reset. This makes the paper supply to the rotatable cassette more troublesome.